The answer to this question is very simple: COVID-19 is caused by a highly contagious agent. And, @Volodymyr Krasnoholovets: you appear to be not very well informed about the origin of the virus. It is worth to read scientific literature.
It started in winter which is the usual flu season so initially, the weather also contributed to the spread of the disease. But later the cultural factors and habits of people are big reasons for the increase in the epidemic of the Corona Virus because people like to mingle socially and they are not habitual of being isolated in quarantine so, in many places, even after government restrictions, people are not good in practicing self-quarantine, as they don't want to stay in their homes for long.
The answer to this question is very simple: COVID-19 is caused by a highly contagious agent. And, @Volodymyr Krasnoholovets: you appear to be not very well informed about the origin of the virus. It is worth to read scientific literature.
Yes! Bad habits, cultural and environmental factors have led to significant increase and spread of the virus. The other day I watched on local TV two guys shaking hands with nk gloves on, no masks on, nothing! This is total ignorance!
Among the many factors we have: the very large increase in world population with a very high density in mega cities and also the increase in the number of (cheap) travels from one continent to another and the mass tourism. All these factors increase the probability of contamination of virus diseases
It is the nature of a highly contagious pathogen to cause a considerable increase of cases, as we currently see.
In principle, a pathogen can be eradicated completely only if humans are the only hosts. This was the case with smallpocks, which were successfully eradicated in the 1970ies through vaccination campaigns organized by WHO. This is also nearly (but not completely) achieved with the poliomyelitis virus. Hepatitis B could also, given a very high coverage of vaccination, be eradicated. Eradication is not possible if animals are primary sources or intermediate hosts of a pathogen. I could provide many examples. SARS-CoV-2 has apparently intermediate animal hosts or even bats as the primary source. It is impossible to control the huge bat population and even an intermediate host has not been convincingly identified. In consequence, we have to wait for the vaccine and carefully study how long immunity will be provided through vaccination(s) and, possibly, in case of mutations of the virus, re-vaccinate after a given period of time (as is the case with the influenza vaccine). Also we have to learn whether antibodies after natural infections are reallly protective, and, if so, for how long they provide protection. Fortunately, mutations occur at a lower rate in SARS-CoV-2 than in influenza viruses.
Coronavirus spreads from person to person through close communities and spreads alarmingly in highly populated cities. At first people were unaware of the disease. So, they did not care much. Lockdown measures should have been taken from the beginning of the spread of the disease to minimize infection.
There are many reasons to increase of Covid19 few are discussed below.
People are not following rules of social distancing. They are taking it lightly.
Government doesn't have required facility to conduct tests.
Labour class peoples doesn't get proper help from government to reach their home towns. Asymptomatic patients are also plays an important role to increase covid 19 infection.
It is the careless and carefree attitude of irresponsible citizens. They are not realizing the effect of the virus, and loss of life. Who is going to educate one and all, for their own life-safety ?